Remaining battery life prediction device and battery pack

Abstract

Provided is a low-cost battery pack capable of predicting a remaining battery life of a rechargeable battery with high accuracy. A remaining battery life prediction device includes: a voltage detection unit configured to measure a battery voltage and a battery temperature of the battery; a calculation unit configured to perform predictive calculation of a remaining battery life based on the battery voltage and the battery temperature; and a control unit configured to control operation of the remaining battery life prediction device and the calculation unit, the remaining battery life prediction device being configured to predict a remaining life of the battery with a calculation flow of for a predetermined time period, recursively calculating the remaining battery life based on the measured battery voltage and battery temperature and an internal impedance of the battery in a battery equivalent circuit.

What is claimed is: 
     
       1. A battery pack, comprising:
 a MOSFET configured to control a load current and a battery connected in series between a first external terminal and a second external terminal to which a load is connected; 
 a control circuit that is connected to both ends of the battery and is configured to monitor a state of the battery and control the MOSFET; and 
 a remaining battery life prediction device connected to both the ends of the battery and configured to predict a remaining life of the battery, the device comprising: 
 a voltage detection unit configured to measure a battery voltage and a battery temperature of the battery; 
 a calculation unit configured to perform predictive calculation of a remaining battery life based on the battery voltage and the battery temperature; and 
 a control unit configured to control operation of the remaining battery life prediction device and the calculation unit, 
 the remaining battery life prediction device being further configured to predict the remaining life of the battery with the calculation unit configured to perform a calculation flow of, for a predetermined time period, recursively calculating the remaining battery life at predetermined intervals based on a currently measured battery terminal voltage and battery temperature, an internal impedance of the battery in a battery equivalent circuit, a last measured battery terminal voltage and battery temperature, and a last calculated remaining battery life and battery open circuit voltage, such that the remaining battery life prediction device does not include a current sensing device connected to the battery. 
 
     
     
       2. The remaining battery life prediction device according to  claim 1 , wherein the battery equivalent circuit comprises:
 a voltage source configured to output a battery open circuit voltage; 
 a first resistor connected to the voltage source in series; and 
 an internal impedance element connected to the first resistor in series and includes a resistor and a capacitor connected in parallel to each other. 
 
     
     
       3. The remaining battery life prediction device according to  claim 2 , wherein the calculation unit is configured to perform the calculation flow that further comprises:
 measuring an initial battery terminal voltage and an initial battery temperature when the battery is mounted; 
 calculating an initial remaining battery life based on the initial battery terminal voltage and the initial battery temperature; 
 measuring the battery terminal voltage and the battery temperature for the predetermined time period; and 
 holding, in a storage device, the currently measured battery terminal voltage and battery temperature and the currently calculated remaining battery life and battery open circuit voltage for the predetermined time period. 
 
     
     
       4. The remaining battery life prediction device according to  claim 2 , wherein the internal impedance in the battery equivalent circuit comprises a plurality of the impedance elements connected in series. 
     
     
       5. The remaining battery life prediction device according to  claim 4 , wherein the calculation unit is configured to perform the calculation flow that futher comprises comprises:
 measuring an initial battery terminal voltage and an initial battery temperature when the battery is mounted; 
 calculating an initial remaining battery life based on the initial battery terminal voltage and the initial battery temperature; 
 setting an initial value to a voltage applied to the impedance element; and 
 holding, in a storage device, the currently calculated remaining battery life and voltage applied to the impedance element for the predetermined time period. 
 
     
     
       6. The remaining battery life prediction device according to  claim 1 , wherein the predetermined time period for which the predictive calculation of the remaining battery life is performed is 2 N  seconds, where N is an integer.